Periarteriolar lymphoid sheaths

Periarteriolar lymphoid sheaths (or periarterial lymphatic sheaths, or PALS) are a portion of the white pulp of the spleen. They are populated largely by T cells and surround central arteries within the spleen; the PALS T-cells are presented with blood borne antigens via myeloid dendritic cells.

In contrast, the lymphoid portions of the white pulp are dominated by B cells.

External links

Histology image: 07703loa – Histology Learning System at Boston University
Histology image: 62_06 at the University of Oklahoma Health Sciences Center
Diagram at okstate.edu
Diagram

Organs of the lymphatic system

Primary organs

Bone marrow	Hematopoietic stem cell
Thymus	Hassall's corpuscles

Secondary organs

Spleen	Parts Hilum Trabeculae Red pulp Cords of Billroth Marginal zone White pulp Periarteriolar lymphoid sheaths Germinal center Blood vessels Trabecular arteries Trabecular veins
Tonsils	Palatine Lingual Pharyngeal Tubal Tonsillar crypts Waldeyer's tonsillar ring
Lymph nodes	Lymphatic vessel T cells High endothelial venules B cells Germinal center Mantle zone Marginal zone
MALT	GALT Peyer's patch Germinal center